ssh: update to OpenSSH v8.8p1

OpenSSH v8.8p1 was motivated primarily by a security update and
deprecation of RSA/SHA1 signatures. It also has a few minor bug fixes.

The security update was already applied to FreeBSD as an independent
change, and the RSA/SHA1 deprecation is excluded from this commit but
will immediately follow.

MFC after: 1 month
Relnotes: Yes
Sponsored by: The FreeBSD Foundation